Canzhu Gao

New strategy for the evaluation of CdTe quantum dot toxicity targeted to bovine serum albumin

The biological toxicity of CdTe quantum dots (QDs) to bovine serum albumin (BSA) has been investigated mainly by fluorescence spectra, UV-vis absorption spectra and circular dichroism (CD) under simulative physiological conditions. Fluorescence data revealed that the quenching mechanism of BSA by CdTe QDs was a static quenching process and the binding constant is 6.05x10(3) and the number of binding sites is 0.7938. The thermodynamic parameters (DeltaH=-62.33 kJ mol(-1), DeltaG=-21.21 kJ mol(-1), and DeltaS=-140.3 J mol(-1) s(-1)) indicate that hydrogen bonds and van der Waals forces between the protein and the QDs are the main binding forces stabilizing the complex. In addition, UV-vis and CD results showed that the addition of CdTe QDs changed the conformation of BSA.

Binding of oxytetracycline to bovine serum albumin: spectroscopic and molecular modeling investigations.

The residue of the widely used veterinary drug oxytetracycline (OTC) in the environment (e.g., animal food, soils, surface water, and groundwater) is potentially harmful. Knowledge of its binding to proteins contributes to the understanding of its toxicity in vivo. This work establishes the binding mode of OTC with bovine serum albumin (BSA) under physiological conditions by spectroscopic methods and molecular modeling techniques. The inner filter effect was eliminated to get accurate data (binding parameters). On the basis of the thermodynamic results and site marker competition experiments, it was considered that OTC binds to site II (subdomain IIIA) of BSA mainly by electrostatic interaction. Furthermore, using the BSA model established with CPHmodels, molecular docking and some other molecular modeling methods were applied to further define that OTC interacts with the Arg 433, Arg 436, Ala 429, and Pro 516 residues of BSA. In addition, UV-visible absorption, synchronous fluorescence, and circular dichroism (CD) results showed that the binding of OTC can cause conformational and some microenvironmental changes of BSA. The work provides accurate and full basic data for clarifying the binding mechanisms of OTC with BSA in vivo and is helpful for understanding its effect on protein function during its transportation and distribution in blood.

Investigation on the toxic interaction of toluidine blue with calf thymus DNA

The gene toxic interactions of toluidine blue (TB) with calf thymus DNA (ct-DNA) were examined in vitro with UV-visible absorption spectroscopy, fluorescence spectroscopy, fluorescence polarization and circular dichroism techniques. The experimental results showed that TB interacted with ct-DNA by two binding modes. At low TB concentrations, TB intercalated into the DNA base pairs. At higher TB concentrations, TB was attached to the negatively charged phosphate groups. For the intercalation binding mode and electrostatic binding mode, the binding constants were 1.76 x1 0(6)L mol(-1) and 6.18 x 10(5)L mol(-1) and the number of binding sites was 0.48 and 0.79, respectively. Circular dichroism results showed that the two binding modes had different effects on the ct-DNA conformation. At high dye concentrations, Z-form DNA appears, while at low TB concentrations, a B to A form transition is observed.

Toxic effects of different charged metal ions on the target--bovine serum albumin.

In this work, the toxic influence of metallic ions (Na+, Cu2+, Al3+) on the serum albumin were studied by fluorescence, resonance light scattering (RLS), synchronous fluorescence, UV-vis absorption and circular dichroism (CD) spectroscopy. The experimental results indicated that ion electric charge is not the main factor affecting the structure of bovine serum albumin (BSA). Na+ made the structure of BSA tighter and hydrophobicity enhanced, which improved fluorescence intensity, while Cu2+ could react with some functional groups of BSA, making the structure of BSA looser, so that the internal hydrophobic groups such as tryptophan (Trp) and other aromatic residues were gradually exposed. When we observed them with fluorescence spectra, we found fluorescence quenching with increasing Cu2+ dose. Al3+ is shown as little significant influence on the BSA, but BSA was found to aggregate with the dose of Al3+ by means of RLS because of the hydrolysis and ion strength effect of Al3+. The results also proved normal saline could keep lives healthy and good-working as a biological humour, however, heavy metals made harmful effects to the body when they exceeded the minimal effect level (MEL), such as Cu2+ chosen in our work.

Study on the Genotoxic Interaction of Methyl Violet with Calf Thymus DNA

By utilizing ultraviolet (UV)-visible absorption spectroscopy, circular dichroism (CD), resonance light scattering (RLS), and transmission electron microscope (TEM) techniques, the toxic interaction of methyl violet (MV) with calf thymus DNA (ctDNA) was investigated at the molecular level. The UV-visible absorption spectra results showed that MV intercalated into ctDNA base pairs at low MV concentrations, while MV was attached to the negative charged phosphate groups at higher concentrations and the binding constant (Kθ25°C) was 1.80 × 103 L mol−1. The absorbency results showed that the genotoxic interaction of MV with ctDNA is under the electrostatic binding mode. MV had strong toxic interaction with ctDNA at 4.0 × 10−5 mol L−1 MV and pH 6.5. The toxic interaction of MV with ctDNA can result in the formation of massive aggregates and change of the ctDNA conformation, which showed a significant linear dose-response relationship.

Probing the interactions between carboxylated multi-walled carbon nanotubes and copper-zinc superoxide dismutase at a molecular level.

In order to evaluate the toxicity of multi-walled carbon nanotubes (MWCNTs-COOH) at a molecular level, the effect of MWCNTs-COOH on antioxidant enzyme copper-zinc superoxide dismutase (Cu/ZnSOD) was investigated using fluorescence spectroscopy, UV/vis absorption spectroscopy, circular dichroism (CD) spectroscopy and isothermal titration calorimetry (ITC). By deducting the inner filter effect (IFE), the fluorescence emission spectra and synchronous fluorescence spectra indicated that there were interactions between MWCNTs-COOH and Cu/ZnSOD. Moreover, the microenvironment of the amino acid residues in the enzyme was changed slightly. The UV/vis absorption and CD spectroscopic results showed appreciable conformational changes in Cu/ZnSOD. However, the results of a Cu/ZnSOD activity determination did not show any significant difference. In other words, MWCNTs-COOH has no significant effect on enzyme activity. The ITC results showed that the binding of MWCNTs-COOH to Cu/ZnSOD was a weak endothermic process, indicating that the predominant force of the binding was hydrophobic interaction. Moreover, it was essential to consider the IFE in fluorescence assays, which might affect the accuracy and precision of the results. The above results are helpful in evaluating the oxidative stress induced by MWCNTs-COOH in vivo.

Spectroscopic Investigations on the Interaction between Carbon Nanotubes and Catalase on Molecular Level

The interactions between well‐dispersed multiwalled carbon nanotubes (MWCNTs) and catalase (CAT) were investigated. The activity of CAT was inhibited with the addition of MWCNTs. After deducting the inner filter effect, the fluorescence spectra revealed that the tryptophan (Trp) residues were exposed and the fluorescence intensities of CAT increased with the increase in the MWCNTs concentration. At the same time, the environment of the Trp residues became more hydrophobic. The results of UV–vis absorption spectroscopy and CD spectra indicated that the secondary structure of CAT had been changed, and the amino acid residues were located in a more hydrophobic environment. Meanwhile, the UV–vis spectra indicated that the conformation of the heme porphyrin rings was changed. The microenvironment of CAT activity sites may be interfered by MWCNTs. This research showed that MWCNTs could not only contribute to the conformational changes of protein but also change the enzyme function.

Synthesis and Characterization of Nano‐Ziconium Dioxide in Recombination Surfactant Association System

This article investigates the influence factors of reagent ratio, pH, stirring intensity, sintering temperature along with ultrasonic wave to particle size, distribution of nanoziconium dioxide in recombination surfactant system. The optimized reagent ratio (wt) of cyclohexan, OP‐10, n‐Amyl alcohol, zircon salt solution are 55%, 17.5%, 17.5%, 10%, respectively. At pH=8.7, the size of nanozirconium oxide has the priority of smaller (<10 nm), narrower particle size distribution and better performance in W/O form.

Determination of pyridinium-1-propane-3-sulphonate and saccharine in bright nickel electroplating bath

Abstract A new method of ultraviolet absorption spectrophotometry was developed for the simultaneous determination of pyridinium-1-propane-3-sulphonate (PPS) and saccharine in bright electroplating bath. The effects of pH, inorganic salt concentration and 1,4-butynediol on the absorbance of PPS and saccharine were studied. This method is rapid and simple, and can be applied to the on site determination of the concentration of PPS and saccharine in the electroplating bath.

Interaction of Cu 2+ , Pb 2+ , Zn 2+ with Trypsin: What is the Key Factor of their Toxicity?

Heavy metals possess great endangerment to environment even human health because of their indissolubility and bioaccumulation. The toxicity of heavy metal ions (Cu2+, Pb2+, Zn2+) to trypsin was investigated by fluorescence, synchronous fluorescence, UV–vis absorption, circular dichroism (CD) spectroscopy, isothermal titration calorimetry (ITC), and enzyme activity assay. The experimental results showed that toxic effect of heavy metal ions was due to their own characteristic, rather than the electric charges of the ion. Zn2+ could not show the obvious toxicity to trypsin, while the structure and function of trypsin was damaged when the enzyme explored to Cu2+ and Pb2+. From the spectra results, we found that Cu2+ would bind with trypsin, which lead to the fluorescence quenched and hydrophobicity increased. Pb2+ could also change the structure and reduce the activity of trypsin in high concentration. In vitro measurement, the toxicity order of heavy metal ions to trypsin is: Cu2+ > Pb2+ > Zn2+. In addition, isothermal titration calorimetry analysis proved that the interactions between Cu2+, Pb2+, Zn2+ and trypsin were all spontaneous and exothermic, which indicated the adverse effect of these heavy metal ions to trypsin.